Method of making single turn core for transformer or the like



June 1, 1965 G. G. SOMERVILLE METHOD OF MAKING SINGLE TURN CORE FOR TRANSFORMER OR THE LIKE 2 Sheets-Sheet 1 Filed Aug. 2, 1963 June 1965 G. G. SOMERVILLE 3,

METHOD OF MAKING SINGLE TURN CORE FOR TRANSFORMER OR THE LIKE Filed Aug. 2, 1963 2 Sheets-Sheet 2 United States Patent 3,186,067 IVIETHOI) 0F MAKING SINGLE TURN CURE FOR TRANSFGRMEII GR THE LIKE Gareth G. Somerville, Pittsiield, Mesa, assignor to General Electric Company, a corporation of New York Filed Aug. 2, 1%3, Ser. No. 299,597

Claims. (El. 29-15557) This invention relates to cores for electromagnetic induction apparatus and, more particularly, to a method of making single turn magnetic cores.

In the magnetic core art, such as the cores which are used in various types of electromagnetic induction apparatus, the core is formed from a number of layers of magnetic strip material. In forming such cores it has been found desirable to wind a single strip of magnetic material about a mandrel or the like to provide a core having the desired number of layers or laminations. These types of wound cores are usually referred to as spirally wound magnetic cores.

As is well understood the magnetic core must be provided with an electromagnetic coil Wound about the core to provide a desired type of induction apparatus. It has generally been found desirable in this field to pre-form the coils and to place them about the winding leg of the core or to lace the wound core about the pre-formed coil. Examples of these cores are shown in Patent No. 2,478,- 029 and Patent No. 2,305,649 respectively. In either case, it is usually necessary to cut the wound core so that it may be assembled with the pre-formed coil.

A number of cut cores are known, such as the single butt joint exemplified by Patent No. 2,478,029 or the staggered or butt lapped joint of Patent No. 2,305,649. In all of the known constructions many problems appear with respect to the ease of manufacture, the noise in the finished core and the amount of losses present in the finished core. This application presents a novel core and method of making the core in which the core is provided with a plurality of staggered joints, of single turn construction, that is, with one joint in each layer or lamination. A core made according to this invention provides better noise and loss characteristics due to freedom from strain, while improving the ease of manufacturing the core.

It is, therefore, one object of this invention to provide a novel single turn core using a plurality of staggered joints.

It is a further object of this invention to provide a novel method of making a single turn, staggered joint core.

A still further object of this invention is to provide a single turn core having a plurality of staggered joints which have low loss characteristics and which are easy to manufacture.

In carrying out this invention in one form a core memher is formed from a single strip of magnetic material wound to provide a plurality of spiral laminations. The wound core is then out along a single radial line forming a plurality of single turn laminations with the outer lamination extending beyond a single turn. The outer lamination is lapped to form the outer lamination of the finished core. The remaining laminations are clamped at one point and then opened, causing the cut ends of one portion to slide into offset relation with respect to each other. A plurality of laminations from the outer portion; that is, the longer laminations, arethen removed and assembled into the lapped outer lamination to provide a plurality of laminations having staggered butt joints. A second group of laminations are then removed and assembled in the outer lamination in the same manner. The staggered joint of the second group is placed in the same area of the core as the staggered joint of the 3,186,067 Patented June 1, 1965 first group. The remaining laminations are assembled in the same manner, the number of groups depending on the total number of laminations. The assembled core is then shaped and annealed to thereby provide a single turn core having a staggered joint.

The invention which it is desired to protect is particularly pointed out and distinctly claimed in the claims appended hereto. However, it is believed that this invention and its objects and advantages, as well as other objects and advantages thereof, will be more clearly understood from the following detailed description of a preferred embodiment thereof, especially when considered in the light of the accompanying drawings, in which:

FIGURE 1 is an elevation view of a wound core showing the clamping and cutting of the preferred embodiment of this invention;

IGURE 2 is an elevation view showing the core of FIG. 1 in its open position, after cutting;

FIGURE 3 is an elevation view illustrating one method of further staggering or offsetting the cut ends of the core;

FIGURE 4 shows the results of the method of FIG. 3;

FIGURE 5 is an elevation view showing the removal of a goup of laminations from the open oifset core of FIGS. 2 or 4;

FIGURE 6 shows the outer lamination of the core member of FIG. 1 used as a stacking ring;

FIGURE 7 shows the manner of assembling a group of laminations from the open core of FIG. 5 into the stacking ring of FIG. 6;

FIGURE 8 shows a tie lamination being assembled with the laminations of FIG. 7;

FIGURE 9 shows a second group of laminations being assembled into the core of either FIG. 7 or FIG. 8;

FIGURE 10 shows the completed stacked core with a plurality of stacked staggered joints;

FIGURE 11 shows a modified form of the stacked core of FIG. 10; and

FIGURE 12 shows the core of FIG. 10 shaped and clamped ready to be annealed.

Referencewill now be made to the drawings, in which like numerals are used to indicate like parts throughout the various views thereof, for a complete description of the present preferred embodiment of the method of making a single turn, staggered joint core according to this invention. However, it will be understood that this description is for illustrative purposes only and that the invention is not limited thereto other than as indicated in the claims appended hereto.

Referring first to FIG. 1 of the drawing, there is shown therein a core member designated 10 comprising a plurality of laminations formed from a single strip of magnetic material. As will be understood the strip material is wound about a mandrel, or the like, normally in circular form in the manner shown in FIG. 1 to form a circular core of the desired number of laminations. The end turn is shown in FIG. 1, and is the end of the outer lamination 12 forming the core member 10. A clamp member 14 is then clamped about a portion of the core tofirmly hold all laminations together, in the manner shown in FIG. 1. Thenthe outer lamination 12 is pulled back away from the core 10 and a cut made on a single radial line, indicated at 16 in the drawing, which radial line is below the pulled back end of the outer lamination 1.2. For example, in the manner shown in FIG. 1, a pinch cutter 18 such as, for example, the pinch cutter shown in the Moody et al. Patent No. 2,947,065 may be used to provide a desired single cut through the entire group of laminations forming the core 10. As will be apparent from FIG. 1, when the core member is completely cut through on the line 16 a plurality of single no turn laminations will be formed by such cut with an outer lamination, indicated at 12, which will be longer than a single turn lamination and which will overlap itself at the point of cutting; that is, along the line 16.

After cutting, the wound laminations of the core 1% are opened in a straight position, as shown in FIG. 2, thereby causing the ends of the laminations opposite the clamp 14 to assume the staggered relation indicated in FIG. 2. As will be apparent, by holding the cut ends of the laminations forming the core It by the clamp 14 in substantially a straight position when the core member ltd is open, in the manner shown in FIG. 2, the opposite ends or" the various laminations will slide with respect to each other thereby forming the offset indicated in FIG. 2. After the core has been opened, as in FIG. 2, clamp 14 is loosened and the outer lamination 12 removed. As will be understood, in some instances it will be found desirable to leave the inner turn of the core 10 uncut, as is indicated by the partial dotted loop 13, in FIG. 2. When the inner turn is not cut, it will also be removed when the clamp 14 is loosened.

In general, it has been found sufiicient to merely open the core member 10 as shown in FIG. 2 to provide a desired offset of the various laminations forming the core 10. It has generally been found sufficient to have an overlap of approximately W when utilizing magnetic core strip material approximately 12 mils in thickness. However, if it should be desired to have a longer overlap than the approximate 7 the overlap may be increased, for example in the manner shown in FIG. 3. In FIG. 3 a second clamp member 2% is placed about the staggered ends of the laminations forming the core 19. With the clamp 14 relaxed, at pressure roll, such as 22, is forced against the laminations near the clamp member 14 to thereby bend the laminations back in the direction of the wound core as shown in FIG. 3. When the stacked laminations forming the core 1% are in the position substantially shown in PEG. 3, clamp 14 is then tightened and clamp 20 is released. If the core is now placed in the straight position shown in FIG. 4 then the ends of the lamination opposite clamp 14 will assume the larger offset indicated in FIG. 4. Of course, it will be understood that if desired the same effect could have been obtained by bringing the core 1% of FIG. 2 beyond the straight position, then tightening the clamp 29 before straightening it out which would of course provide the offset similar to FIG. 4 rather than the offset of FIG. 2. Alternatively, the offset can be increased, if desired, when groups of laminations are removed from core 16 in the manner indicated in FIG. 5. The bending of the laminations away from core it) will increase the offset of the ends.

FIGURE 5 is a showing of the laminations forming the core member after the desired offset between the various laminations has been obtained, that is, the offset of either FIG. 2 or of FIG. 4 as desired. A clamp member 24- is provided, generally in the form of a pair of pressure rollers, as indicated in PEG. 5, which loosely clamp the stacked laminations together. When ready to assemble the core within the stacking ring, a group of laminations, for example to laminations, are removed from the outer portion of the stack of laminations forming the core 10 in the manner indicated at 26 thereby forming a group of laminations indicated by the numeral 28.

Referring now to FIG. 6' of the drawing the original outer lamination, indicated at 12 in FIG. 1, is removed from the core as earlier mentioned. The lamination 12 is formed into a stacking ring of the correct size having overlapped ends as indicated at 34 The overlapped ends are welded or clamped as desired to securely hold the outer lamination to the desired size. As can be seen from FIG. 6, this fixes the outer size of the finished core and forms what may be termed the stacking ring for stacking the cut core to form the desired single turn out core of this invention.

Referring now to FIG. 7, it is seen that the outer lamination 12 has placed therein the group of laminations 28 which had been removed from the stack 16 of FIG. 5. As will be apparent from FIG. 7, the outer laminations readily fit into the stacking ring 12, in general tending to overlap on themselves. However, the inner few sheets, as indicated at 32, are fitted against their respective butt ends as indicated in PEG. 7. Then by means of pressure, in the direction of the arrow 34, the laminations may be forced into the circular position of the outer stacking ring 12. The pushing of the members 32 will cause the remaining portions of the group 23 to drop into their proper positions forming a plurality of staggered butt joints as is indicated at 36 in PEG. 8.

The staggered butt joint of this invention has been found to provide excellent magnetic and noise levels. However, it has been found to have very little mechanical strength. Therefore, when used in induction apparatus requiring cores of mechanical strength it is generally desirable to add a tie sheet after each group of laminations.

FIGURE 8 shows the method of inserting the tie sheet into the portion of the formed core of FIG. 7. As is shown in FIG. 8, the outer lamination 12 and the group of laminations 28 are formed into a circular core memher having the staggered joint, generally indicated at 36. The next lamination 38 is then taken from the bottom of the stack of laminations of FIG. 5 and is inserted into the formed core of PEG. 8. The ends of the lamination are butted against each other in the same manner as the laminations 32 of FIG. 7 and then by pressure in the direction of the arrow 40' the lamination is caused to move into the circular shape of the outer lamination 12 and the group of laminations 28 forming a tight, butt joint. As is shown in FIG. 8, in adding the tie sheet 38 it is desirable to provide the butt joint on the opposite side of the core from the staggered butt joint 36. It is preferable that this be 180 removed from the main joint 36, in the manner indicated in FIG. 8. However, as will be understood, increased mechanical strength can be obtained when the joint of the tie sheet is in another area of the core, for example removed from the joint 36. By use of the tie sheet it is found that substantial mechanical strength may be added to the core member, when desired.

Refering now to FIG. 9 of the drawing, a second group of laminations indicated at i2 are then removed from the bottom of the stack of laminations of HG. 5 and are inserted into the circular core of FIG. 8 in the same manner as the first group of laminations Again, most of the laminations will overlap on themselves but the outer few laminations are fitted against their butt ends in the manner shown in FIG. 9 and then pressure in the direction of the arrow 44 will cause the laminations to assume the circular position of the rest of the core and will cause all the laminations of the group 42 to drop into proper position forming a plurality of staggered butt joints in the same manner as the butt joints formed in FIG. 7.

The above procedure may be continued, utilizing a plurality of groups of laniinations of approximately 15 or 20 laminations until all of the laininations have been stacked into tle stacking ring 12 with the plurality of staggered butt joints as indicated in FIGS. 7 and 9. If desired, the tie sheets, such as 3-8 of PEG. 8, may be added in after each group or may be added in after a plurality of groups, as desired, according to the necessary mechanical strength of the completed core. After all of the groups of laminations have been assembled into the Stacie ing ring 12 a final core member is obtained as shown in PEG. 10.

FIGURE 10 shows the use of four separate groups of laminations with two separate tie members, the groups being indicated at 28, 42, ie and 43, while the two tie sheets are indicated at 38 and 5%. After the entire core is assembled the area of the core having the staggered the ability of the assembler.

butt joints is then clamped tightly by means of a clamp 52, as indicated in FIG. 10. The assembled core memher is then pressed in the desired shape, normally rectangular, as shown in FIG. 12, by means of a plurality of clamps and it is then ready to be annealed.

in some types of cores, for example, large induction cores, it is undesirable to assemble a single tie sheet, because of the time required to perform such assembly. In order to eliminate the tie sheet and still improve the mechanical strength of the core, the staggered butt joints may be alternately arranged on opposite sides of the core as shown in MG. 11. FIGURE 11 shows the use of four separate groups of laminations used to form the desired core. However, in this instance the tie sheets are eliminated. Instead, as shown the butt joint of the outer group 28 is in the lower end of the core While the butt joint of group 42 is at the upper end of the core. In the same manner, the butt joints of groups 46 and 48' are alternated, with the butt joints of group 46 at the lower end and the butt joint of group 48 at the upper end. By this construction the mechanical strength is improved without the use of tie sheets. Of course, it will be understood that it is not necessary that the alternate butt joints be on opposite sides of the core, as shown in FIG. 11. If desired, each butt joint could be spaced approximately 90 from its preceding butt joint. Obviously, such construction would also increase the strength of the core. After the complete core has been assembled, it will be pressed into a desired shape for annealing, as shown, for example, in FIG. 12.

As will be apparent to those skilled in the art, by cutting and forming the entire core in the manner disclosed in this application prior to the anneal any of the stresses which are built up in the core steel during the cutting and shaping or forming of the core member will be relieved by the annealing step. After the core has been annealed in the desired shape the core may then be taken to an assembly area where an assembler may insert the sheets either a pack at a time or a number of la-minations from a pack depending upon the type of core being made, the size of the pre-formed coils and Thus as will be apparent by means of this invention a single turn, staggered joint core has been provided having excellent magnetic and noise characteristics and which is relatively easy to manufacture.

While there has been shown and described the present preferred embodiment of the invention, it will be apparent to those skilled in the core-making art that various changes may be made in the steps set forth herein without departing from the invention. For example,-the number of sheets in each group can be varied as desired to suit the size and shape of the particular core. Also the various tie sheets may be added, as desired, according to the mechanical strength necessary to the core or may be left out entirely. Thusit will be understood that the foregoing description is for illustrative purposes only and that the invention set forth herein is limited only in the manner required by the appended claims.

What is claimed as new and which it is desired to secare by Letters Patent of the United States is:

1. A method of making'a single turn staggered joint magnetic core comprising:

(a) forming a core by spirally winding a plurality of layers of magnetic material,

(b) clamping the wound layers of said core,

(0) lifting the end portion of the outer layer of said formed core, then cutting said formed core along a single radial line below said end portion of said outer layer,

(d) opening said formed core causing the free ends of said layers opposite said clamp to become offset with respect to each other, relaxing said clamp about said layers,

(e) removing said outer layer from said core,

(1) forming said outer layer into a desired size having a lapped joint and securing said lapped joint,

(f) removing a group of layers from the outer portion of said remaining layers,

( 1) assembling said group of layers within said outer layer with the cut ends forming staggered butt points,

g) removing the next single outer layer from said remaining layers,

(1) assembling said single layer within said group of layers with the cut ends of said single layer forming a butt joint opposite to said staggered butt joints of said group of layers,

(h) removing another group of layers from said remaining layers,

(1) assembling said another group within said single layer with the cut ends of said another groups forming staggered butt joints adjacent to said staggered butt joints of said group of layers and opposite to said butt joint of said single layer,

(i) removing another single layer from the outer portion of said remaining layers,

(l) assembling said another single layer within said another group of layers with the cut ends of said single layer forming a butt joint opposite to said staggered butt joints of said another group of layers,

(j) continuing alternately to assemble groups of layers and single layers until all layers have been assembled within said outer layer,

(k) shaping said assembled core to the desired core shape, and

(l) annealing said shaped assembled core.

2. A method of making a single turn staggered joint magnetic core comprising:

(a) forming a core by spirally winding a plurality of layers of magnetic material,

(b) clamping the wound layers of said core,

(c) lifting the end portion of the outer layer of said formed core, then cutting said formed core along a single radial line below said end portion of said outer layer,

(d) opening said formed core causing the free ends of said layers opposite said clamp to become offset with respect to each other, relaxing said clamp about said layers,

(e) removing said outer layer from said core,

(1) forming said outer layer into a desired size having a lapped joint and securing said lapped joint,

(f) removing a first group of layers from the outer portion of said remaining layers,

(1) assembling said group of layers within said outer layer, with the ends forming staggered butt joints,

(g) removing another group of layers from said remaining layers,

(1) assembling said another group within said first group of layers with the ends of said another group forming staggered butt joints adjacent to saidstaggered butt joints of said first group of 7 layers,

(h) removing a single layer from the outer portion of said remaining layers,

(1) assembling said single layer within said another group of layers with the cut ends of said single layer forming a butt joint opposite to said staggered butt joints of said another group of layer (i) continuing alternately to assemble groups of layers and single layers until all layers have been assembled within said outer layer,

(j) shaping said assembled core to the desired core shape, and

(k) annealing said shaped assembled core.

3. A method of making a single turn staggered joint magnetic core comprising:

(a) forming a core by spirally winding a plurality of layers of magnetic material,

(b) clamping the wound layers of said core,

() lifting the end portion of the outer layer of said formed core, then cutting said formed core along a single radial line below said end portion of said outer layer,

(d) opening said formed core causing the free ends of said layers opposite said clamp to become offset with respect to each other, relaxing said clamp about said layers,

(e) removing said outer layer from said core,

(1) forming said outer layer into a desired size having a lapped joint and securing said lapped joint,

(f) removing a first group of layers from the outer portion of said remaining layers,

(1) assembling said group of layers within said outer layer with the ends forming staggered butt joints,

(g) removing another group of layers from said remaining layers,

(1) assembling said another group Within said first group of layers with the ends of said another group forming staggered butt joints spaced from said staggered butt joints of said first group of layers,

(h) continuing to assemble groups of layers with the cut ends of each group forming staggered butt joints spaced from the staggered butt joints of adjacent groups until all layers have been assembled Within said outer layer,

(i) shaping said assembled core to the desired core shape, and

(j) annealing said shaped assembled core.

4. A method of making a single turn staggered joint magnetic core comprising:

(a) forming a core by spirally winding a plurality of layers of magnetic material,

(b) clamping the wound layers of said core,

(c) lifting the end portion or" the outer layer of said formed core, then cutting said formed core along a single radial line below said end portion of said outer layer,

(d) opening said formed core causing the free ends of said layers opposite said clamp to become olfset with respect to each other, relaxing said clamp about said layers,

(e) removing said outer layer from said core,

(1) forming said outer layer into a desired size having a lapped joint and securing said lapped joint,

(f) removing a group of layers from the outer portion of said remaining layers,

(1) assembling said group of layers Within said outer layer, with the ends forming staggered butt joints,

(g) removing the next single outer layer from said remaining layers,

(1) assembling said single layer within said group 5e; of layers with the cutt ends of said single layer forming a butt joint spaced from the staggered butt joints of said group of layers,

(h) removing another group of layers from said remaining layers,

(1) assembling said another group within said single layer with the cut ends of said another group forming staggered butt joints adjacent to said staggered butt joints of said group of layers,

(i) removing another single layer from the outer portion of said remaining layers,

(1) assembling said another single layer Within said another group of layers with the cut ends of said single layer forming a butt joint spaced from said staggered butt joints of said another group of layers,

(j) continuing alternately to assemble groups of layers and single layers until all layers have been assembled Within said outer layer,

(k) shaping said assembled core to the desired core shape, and

(l) annealing said shaped assembled core.

5. A method of making a single turn staggered joint magnetic core comprising:

(a) forming a core by spirally winding a plurality of layers of magnetic material,

(b) clamping the wound layers of said core,

(c) lifting the end portion of the outer layer of said formed core, then cutting said formed core along a single radial line below said end portion of said outer layer,

(d) opening said formed core causing the free ends of said layers opposite said clamp to become offset with respect to each other, relaxing said clamp about said layers,

(e) removing said outer layer from said core,

(1) forming said outer layer into a desired size having a lapped joint and securing said lapped joint,

(f) removing a first group of layers from the outer portion of said remaining layers,

(1) assembling said group of layers within said outer layer with the ends forming staggered butt joints,

(g) removing another group of layers from said remaining layers,

(1) assembling said another group within said first group of layers with the cut ends of said another group forming staggered butt joints opposite to said staggered butt joints of said first group of layers,

(h) continuing to assemble groups of layers having alternating staggered butt joints until all layers have been assembled Within said outer layer,

(i) shaping-said assembled core to the desired core shape, and

(j) annealing said shaped assembled core.

Rei'erences flirted by the Examiner UNITED STATES PATENTS 2,973,494 2/61 Ellis 336217 3,066,388 12/62 Cooper 29-155.6X

JOHN F. CAMPBELL, Primary Examiner. 

4. A METHOD OF MAKING A SINGLE TURN STAGGED JOINT MAGNETIC CORE COMPRISING: (A) FORMING A CORE BY SPIRALLY WINDING A PLURALITY OF LAYERS OF MAGNETIC MATERIAL, (B) CLAMPING THE WOUND LAYERS OF SAID CORE, (C) LIFTING THE END PORTION OF THE OUTER LAYER OF SAID FORMED CORE, THEN CUTTING SAID FORMED CORE ALONG A SINGLE RADIAL LINE BELOW SAID END PORTION OF SAID OUTER LAYER, (D) OPENING SAID FORMED CORE CAUSING THE FREE ENDS OF SAID LAYERS OPPOSITE SAID CLAMP TO BECOME OFFSET WITH RESPECT TO EACH OTHER, RELAXING SAID CLAMP ABOUT SAID LAYERS, (E) REMOVING SAID OUTER LAYER FROM SAID CORE, (1) FORMING SAID OUTER LAYER INOT A DESIRED SIZE HAVING A LAPPED JOINT AND SECURING SAID LAPPED JOINT, (F) REMOVING A GROUP OF LAYER FROM THE OUTER PORTION OF SAID REMAINING LAYERS, (1) ASSEMBLING SAID GROUP OF LAYERS WITHIN SAID OUTER LAYER, WITH THE ENDS FORMING STAGGERED BUTT JOINTS, (G) REMOVING THE NEXT SINGLE OUTER LAYER FROM SAID REMAINING LAYERS, (1) ASSEMBLING SAID SINGLE LAYER WITHIN SAID GROUP OF LAYERS WITH THE CUT ENDS OF SAID SINGLE LAYER FORMING A BUTT JOINT SPACED FROM THE STAGGERED BUTT JOINTS OF SAID GROUP OF LAYERS, (H) REMOVING ANOTHER GROUP OF LAYERS FROM SAID REMAINING LAYERS, (1) ASSEMBLING SAID ANOTHER GROUP WITHIN SAID SINGLE LAYER WITH THE CUT ENDS OF SAID ANOTHER GROUP FORMING STAGGERED BUTT JOINT ADJACENT TO SAID STAGGERED BUTT JOINT OF SAID GROUP OF LAYERS, (I) REMOVING ANOTHER SINGLE LAYER FROM THE OUTER PORTION OF SAID REMAINING LAYERS, (1) ASSEMBLING SAID ANOTHER SINGLE LAYER WITHIN SAID ANOTHER GROUP OF LAYERS WITH THE CUT ENDS OF SAID SINGLE LAYER FORMING A BUTT JOINT SPACED FROM SAID STAGGERED BUTT JOINTS OF SAID ANOTHER GROUP OF LAYERS, (J) CONTINUING ALTERNATELY TO ASSEMBLE GROUPS OF LAYERS AND SINGLE LAYERS UNTIL ALL LAYERS HAVE BEEN ASSEMBLED WITHIN SAID OUTER LAYER, (K) SHAPING SAID ASSEMBLED CORE TO THE DESIRED CORE SHAPE,AND (L) ANNEALING SAID SHAPED ASSEMBLED CORE. 